There are many advantages to the use of light emitting diode (LED) die packages as light sources in light fixtures to produce light efficiently. Many light fixtures have incorporated arrays of LED light sources often configured in a bar-shaped housing or module (also referred to as a “light bar” or LightBAR™).
A light bar often includes an extruded or die-cast bar of aluminum or other thermally conductive material to which the LEDs are bonded directly. This heat dissipating carrier to which the LEDs are attached is typically made of metal, such as a heat conductive aluminum alloy, and may provide heat dissipation to allow proper cooling of the LED, or may have an additional heat sink or other heat dissipating means attached. In most light bars the printed circuit board connects the LEDs to a power source. Often the circuit board is laminated to the extruded or die-cast bar. The light bars may further include circuitry to drive the LEDs included in one or more arrays of LED light sources. Typically, the LED arrays are made up of LED die packages that each include an LED light source with a lens (or primary optic), where each of the LED die packages are in turn associated with an optical system (or secondary optic) to control and/or maximize the light emitted from the LED package. In other configurations the LED light source may only have one over-optic to refract light. The light bars may further include circuitry to drive the LEDs included in the array. Each of the secondary optics aligned with the LED light source may be varied in shape and/or individually rotated to create a beam pattern for the array that is unique from the devices themselves, including all degrees of freedom, e.g. separately determined translation, tilt, and yaw for each lens. The array could comprise similarly colored LEDs, white or otherwise, or various colored LEDs.
Light bars are often shown as a rectangular flat bar, but can assume any two dimensional planar shape, such as square, circular, hexagonal, triangular or an arbitrary free-form shape. The light bar, either individually or combined with other light bars, can be the basis of a luminaire that is used for street lighting, pathway lighting, parking structure lighting, decorative lighting and any other type of spread beam application. With the heat sinking and power incorporated on or into the light bar, the light bar can be incorporated into existing luminaires or integrated into new luminaire designs.
Light bars provide the ability to generate a particular beam pattern with an array of LEDs which are mounted on a flat or planar plate, which most likely would be parallel to the street or floor. Light bars also provide thermal and electrical distribution required for the LEDs as well as provide means for protecting the array of LEDs from environmental damage. Conventional methods of sealing against water and dust intrusion for the coupling of the LED die package and the secondary optical system have included the use of elastomers (e.g., silicone adhesives) in combination with gasketing material along the entire interior of the light bar. However, the process typically includes several layers to insure a good seal. These multiple layers and the inclusion of the gasket material along the majority of the interior results in a light bar that must have a greater depth. The increased depth cause the cover portion of the light bar to be higher in relation to the positioning of the individual LEDs. This results in a portion of the light being emitted by the LEDs to be cut-off and not distributed to the illuminated area.